The Tongan government has officially announced the death of the King's nephew, Prince Tu'ipelehake, paving the way for the country to go into mourning.
The prince - who worked with commoners towards democratic reform - was killed in a car accident in San Francisco last night with his wife Princess Kaimana.
The two were killed when a teenage driver hit their vehicle at high speed at Menlo Park near Palo Alto.
The Chief Secretary to Cabinet, Eseta Fusitua, says that while the nation is stunned by the tragedy, the government has little part to play in its aftermath.
"All the government does is to announce the tragedy and tradition just swings into place, so that the mourning period and the funeral observations of a royal funeral, all of those just kick into place."
The prince was in America to speak with expatriates in his role as the head of the National Committee for Political Reform.